Go-Kart - i accidently found it and i was so happy
okay, so i can't describe it well
but, if you remember the mission when you chase og loc, the place where the mission ends is the place of the Go-Kart
i will check it again and correct myself if im wrong

Slamvan - i'd say Cheetah is a problem, not Slamvan
you just have to cruise around the strip, vinewood, lowrider meeting vicinity

Cargobo - correct me if im wrong, but - santa maria beach near the lighthouse, near the place where the "beat the cock"-aton starts
im pretty sure that's cargobob

Mothership - two ways(excluding cheats)
1. Are u going to San Fierro? - when you take down the chopper, kill TT and take the car
2. Riot - you'll be spawned where the garage is and Sweet's Greenwood, Cesar's Savanna and Truth's Mothership will be spawned, all unlocked
i dont think they're something-proof, but this is also another way to get to Cesar's Savanna

Tampa - Tampa's pretty hard to find but i know two places where you can get it
1. San Fierro road that stretches from the docks to jizzy's bar - should find it there
2. LS, used car lot near Jefferson's motel - possibility of finding it there - 90%

if Euros hasn't been cleared out, it's in lv, under the camel toe i think